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 A152455 a(n) = minimal integer m such that there exists an m X m integer matrix of order n. 2
 0, 1, 2, 2, 4, 2, 6, 4, 6, 4, 10, 4, 12, 6, 6, 8, 16, 6, 18, 6, 8, 10, 22, 6, 20, 12, 18, 8, 28, 6, 30, 16, 12, 16, 10, 8, 36, 18, 14, 8, 40, 8, 42, 12, 10, 22, 46, 10, 42, 20, 18, 14, 52, 18, 14, 10, 20, 28, 58, 8, 60, 30, 12, 32, 16, 12, 66, 18, 24, 10, 70, 10, 72, 36, 22, 20, 16, 14 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS FORMULA a(1)=0, a(2)=1. If n mod 4 eq 2 then a(n)=a(n/2). Otherwise a(n) = sum (pi-1)*pi^(ei-1) where n = p1^e1*p2^e2*...pk^ek is prime factorization of n. PROG (MAGMA) a := function(n) if n le 2 then return n-1; end if; if n mod 4 eq 2 then n := n div 2; end if; f := Factorization(n); return &+[(t[1]-1)*t[1]^(t[2]-1):t in f]; end function; CROSSREFS See A080737 for another version. - N. J. A. Sloane, Dec 05 2008 Sequence in context: A277030 A011773 A080737 * A293484 A000010 A003978 Adjacent sequences:  A152452 A152453 A152454 * A152456 A152457 A152458 KEYWORD easy,nonn AUTHOR W. R. Unger (billu(AT)maths.usyd.edu.au), Dec 04 2008 STATUS approved

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Last modified October 19 14:21 EDT 2018. Contains 316362 sequences. (Running on oeis4.)